Various optically active quaternary ammonium salts having a high utility value as an asymmetric phase-transfer catalyst have been proposed. In particular, compounds having an optically active 6,7-dihydro-5H-dibenzo[c,e]azepine skeleton is useful. As examples of such compounds, there are the following compounds: a compound represented by the following formula (L-1a) described in Patent Document 1,
(wherein * represents optical activity, i.e., that one axially asymmetric isomer is present in excess of the other axially asymmetric isomer with respect to a bond axis that constitutes the biphenyl structure of the compound); a compound represented by the following formula (L-1b) described in Patent Document 2,
(wherein * has the same meaning as above); a compound represented by the following formula (L-1c) described in Non-Patent Document 1,
(wherein * has the same meaning as above); a compound represented by the following formula (L-1d),
(wherein * has the same meaning as above), etc. All of these catalysts are highly useful for monoalkylation of glycine derivatives. Specifically, for example, when a compound represented by formula (L-1b) was used as a catalyst in an asymmetric monoalkylation reaction represented by the following formula (M-1),
(wherein ** represents optical activity, i.e., that, of the two types of mirror-image isomers present on the carbon atoms shown by **, one isomer is present in excess of the other isomer), the reaction was completed with a minute amount of catalyst (S/C=10,000 (S: substrate mol, C: catalyst mol) even if inexpensive potassium hydroxide was used as a base, and the optical purity of the product was 96% ee.
In contrast, when an asymmetric dialkylation reaction represented by the following formula (M-2),
(wherein ** has the same meaning as above), which is a similar reaction as the above reaction, was performed using the same catalyst and very expensive cesium hydroxide as a base, a large amount of catalyst (S/C=100) was required, although a good optical yield was obtained (Patent Document 2). In Patent Document 3, the reaction of the above formula M-2 was performed using as a catalyst a compound having the azepine skeletone represented by the following formula (L-2),
(wherein * has the same meaning as above), to obtain a similar result.
More specifically, all of the conventional optically active 6,7-dihydro-5H-dibenzo[c,e]azepine skeleton compounds had a problem, to be used as a catalyst for an asymmetric dialkylation reaction.